Metal pickling process



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Patented Nov. 20, 1934 UNITED STATES PATENT OFFICE METAL PICKLmG PROCESS No Drawing. Application August 10, 1932, Serial No. 628,275. In Germany August 14, 1931 10 Claims.

The present invention relates to the cleaning and preservation of metallic surfaces wherein the metal is in contact with a liquid of an acid nature. More particularly, the invention relates to the prevention of excessive pitting and embrittlement of a metal when subjected to a pickling process by treatment with a dilute solution of a non-oxidizing acid.

' Certain objects of the present invention are to prevent the acid pickle liquor from attacking clean portions of the surface of a metal; to obviate over-pickling, embrittlement and pitting of the articles treated; to minimize the amount of metal lost in pickling; to increase the efiiciency of the pickling operation; to prolong the effective life of the pickling bath; and particularly to facilitate the pickling operation. Other and further objects of the invention will be apparent from the following description and accompanying table.

In the art of pickling, the metal is treated with a dilute acid to remove oxides such as rust, scale. and other deposits, after which the metal is preferably washed with water and dipped into "an alkaline bath to remove the last traces of free acid. The acid removes the rust and scale, but unfortunately, from the pickling standpoint, unless some agent to prevent such action is present, it attacks the cleaned metal itself thereby causing loss of metal and producing an evolution of hydrogen as, which escapes into theain carrying with it a fine spray cifthje afi d l ia uor frorn'fii pickling bath and'pi'ififi'c'ihi'aii'atnfdsphere possessing corrosive properties and one which is injurious to health and damaging to equipment.

By the present invention, these objectionable features of the pickling process are substantially overcome or reduced to a minimum. To accomplish to as great an extent as possible the objects set forth in accordance with the presentinvention, there is added to the pickling bath, a regulating agent or ingredient which acts to restrain the action of the acid from attacking clean metal but assists in removing the rust, scale and other deposits, or in other words the regulator or inhibitor causes the acid selectively to remove such materials without appreciably attacking the clean portions of the metal under treatment.

The pickle regulator or inhibitor as disclosed in the present application, comprises an organlfi ides to sulfoxide. The followingsulmxides have proved Ty effective as solvent i lilntor: bgngyl: sulfoxide, dibenzylsulfoxide, diphenylenesulfoxide, polymerized diethylenesulfoxide, thioanthrenesulfoxide. of e aliphatic N mustang-pe m metal'iicklifi'g.

The sulfoxidesmaybe employed as inhibitors with advantage in a number of operations, as for example, in the commercial pickling of iron and steel, in the removal of rust of corrosion products from the interior of piping where it is inconvenient to dismantle the piping, in the preparation of metals for electroplating where it is desirable to remove oxides and other corrosion products without removing the free metal and particularly without injuring the surface of the metal. We have found the sulfoxides to be very efiicient inhibitors where employed in the acid treatment of ferrous metals, but also in the treatment of otmals, such as g1 hf tin afidfi'llifiiinium.

The amount of inhibitor employed will, of course, vary in accordance with the requirements of the operator. For example, in the pickling of heavy, cheap materials, such as, for instance, iron castings, an inhibition of '75 to 90% might be quite satisfactory to the pickler, while in the case of relatively valuable material, such as the finer grades of iron or seamless tubing, the pickler might be dissatisfied with less than 99% or even better inhibition. The amount of inhibition varies somewhat with the kind and amounts of inhibitor employed, although any measurable quantity of inhibitor will produce some retardation of solution.

It is sometimes advantageous to mix with the as of the aromatic series In enera l a ll prg anic,snlfoxides t5 as well inhibitor a substance which will aTise the former ttTreadflybecome wet with acid, or which will tend to disperse -1 quickly and thoroughly throughout the acid. Any of the substances ordinarily used for dispersing materials in an acid medium may be applied, such for example as cell ,sulfi.te pitch, Turkey red oil,

Twitc ells reagent, aldehyde condensation products of naphthol sulfonic acids, petroleum sludge acids. some of the higher aldehydes, watersglnble EaEbohydrates, etc.

The following table shows the results of some tests made with the addition of different sulfoxpickling baths at different temperatures.

The tests were performed by using band iron pieces of 8x1.6x0.075 cm. and having a weight of about 5 grams; as acidfllccs pf sulfuric acid ofnzofizujoncentration weiexmployed and iiftestwas executed with.0.l% of sulfoxide calciflated on the metal.

- Reaction Temper- Decrease Kind oisulioxide me time inweigm Hour: C. Grams Benzylsulfoxide 2 60 0.02

cancm-s-cmmm 2 s0 0.025

Di henylsulfoxide 8.mso.m g 88 3g Diphenylenesulioxide 2 60 0. 02

\ S II 0 x Pol erized diethylenesulloxide Hrs-01 Z 33 $31.,

Thioanthrenesulioxide 2 60 0. 04

O \O E No addition l 27 A test executed with only 0.01 gram of a sulfoxide gave the following result:

We do not wish to be limited to the specific sulfoxides listed above, which it should be understood are given only as examples; nor do we wish to be limited to the amounts of inhibitor or conditions under which the inhibitor is used Nor do we wish to be limited to any particular acid since any acid normall q operations ma m On the contr ry, esire our invention to be limited only as defined in the appended claims:

We claim:-

1. The process of treating metals, which comprises subjecting the metal to a non-oxidizing acid solution containing an organic sulfoxide.

2. The process of treating metals, which comprises subjecting the metal to a non-oxidizing acid solution containing an aromatic sulfoxide.

3. The process of treating metals, which comprises subjecting the metal to a non-oxidizing acid solution containing benzylsulfoxide.

4. The process oi treating metals, which comprises subjecting the metal to a non-oxidizing acid solution containing an aliphatic sulfoxide.

5. The process of treating metals, which comprises subjecting the metal to a non-oxidizing acid solution containing polymerized diethylenesulfoxide.

6. A solution of the type adapted for the acid treatment of metals which contains an organic 10. A solution of the type adapted for the acid treatment of metals which contains polymerized diethylenesulfoxide.

, ALBERT KLAMROTH.

HANS AHRENS. 

